Fig. 1. Calculation results of relationship between central wavelength of reflection spectrum and filling coefficient based on analytic prediction model

Fig. 2. Finite element prediction model. (a) Schematic diagram of finite element prediction model; (b) 3D finite element prediction model; (c)-(e) cross sectional views of layer A, layer B, and layer C of face centered cubic (111) surface; (f) minimum element finite element prediction model

Fig. 3. Calculation results of reflection spectra of TE wave and TM wave obtained by finite element model

Fig. 4. Calculation results of reflection spectrum based on finite element prediction model. (a) Reflection spectra corresponding to particle refractive index of 2.4, 2.6, and 2.8; (b) reflection spectra corresponding to solvent refractive index of 1.2, 1.4, and 1.6

Fig. 5. Calculation results of reflection spectra based on finite element prediction model

Fig. 6. Calculation results of reflection spectra based on finite element prediction model

Fig. 7. Calculation results of reflection spectra based on finite element prediction model. (a) Reflection spectra corresponding to transversal spacing of 200 nm, 220 nm, and 240 nm; (b) reflection spectra corresponding to longitudinal spacing of 200 nm, 220 nm, and 240 nm

Fig. 8. Calculation results of reflection spectrum and electric field distribution based on finite element prediction model. (a) Reflection spectrum corresponding to different longitudinal spacing when particle diameter is 120 nm; (b) distribution of H_z at wavelength of 680 nm with longitudinal spacing of 224 nm; (c) distribution of E_z at wavelength of 680 nm with longitudinal spacing of 224 nm

Fig. 9. Schematic diagrams of sandwiched electrochromic sample model. (a) Before applying voltage; (b) after applying voltage

Fig. 10. TEM results and HAADF-STEM results of fabricated Fe₃O₄@SiO₂ nanoparticles (all scale bars are 50 nm). (a) TEM image of Fe₃O₄@SiO₂ nanoparticles; (b)-(e) distributions of oxygen, silicon, iron, and their fusion elements under high angle ring dark field scanning transmission electron microscopy

Fig. 11. Test results of prepared sandwiched electrochromic sample. (a) Test photos under 0 V, 2.5 V, and 3.5 V voltages; (b) reflected spectra at 0 V, 2.5 V, and 3.5 V